1.3.0 Environmental Assessment

1.3.0 ENVIRONMENTAL ASSESSMENT

(A) Pursuant to the City of Austin's Land Development Code (LDC), Section 25-8- 121, and except to the extent that any of the following requirements are excluded by the Director as provided in Section 25-8-121 (D), an environmental assessment and COA Critical Environmental Feature Worksheet (hard copy and electronic format – cd, diskette, or other media) shall be submitted as detailed below to the director of Watershed Protection and Development Review for proposed development located:

(1) over a karst aquifer

(a) provide a Edwards Aquifer recharge zone map with site location, using the most current information

(b) provide site specific geological map showing bedrock units at a scale of 1”=400’

(2) within an area draining to a karst aquifer or reservoir

(a) provide a contributing zone map to Edwards Aquifer recharge zone

(b) provide site specific geological map showing bedrock units at a scale of 1”=400’

(3) in a water quality transition zone (WQTZ) provide a site map or reference in the site plan application of all WQTZ boundaries (can combine with CWQZ, and floodplain map)

(4) in a critical water quality zone (CWQZ) provide a site map or reference in the site plan application of all CWQZ boundaries (can combine with WQTZ, and floodplain map)

(5) in a floodplain

(a) provide a site map or reference in the site plan application packet of floodplains defined by FEMA (can combine with CWQZ, and WQTZ map)

(b) provide a site map of the COA floodplains in all water courses up to 64 acres of drainage (combined with FEMA floodplains)

(6) on a tract with a gradient of more than 15 percent provide a site map or reference in the site plan application all areas with over 15 percent slopes.

(7) An applicant requesting that information be excluded from an environmental assessment, as provided in Section 25-8-121 (D), shall provide the following information to the Director: (a) documentation that the designated City geologist and wetland biologist have visited the site and concur with the applicant that the environmental assessment information is not necessary

(b) documentation that the site is not located over the Northern or Barton Springs Segments of the Edwards Aquifer

(c) documentation that no known environmental variance to Austin’s Land Development Code, Section 25-8, will be required to accomplish the proposed development of the property.

(B) An environmental assessment (EA) must:

(1) Identify critical environmental features (CEFs) and propose protective measures for the features. All CEFs must be shown on a site map with proposed setbacks, with site topography contour elevation interval of 2 feet, at a scale of no greater than 1”=200’. Photographs of identified features and site conditions are encouraged to assist in evaluation by City staff.

All CEF locations must be entered in the COA Critical Environmental Feature Worksheet supplied with application material. Locations must be accurate and presented as latitude and longitude coordinates (WGS 1984 datum).

EA sections identifying geological CEFs, i.e., CEFs listed in subsection (a)-(e) below, must be prepared by a Licensed Professional Geoscientist in the State of Texas if the site is located over the Edwards Aquifer Recharge Zone, as defined by the City of Austin.

Specific requirements for feature types are as follows:

(a) springs

1. are defined as points or zones of natural groundwater discharge in upland and/or riparian zones which produce measurable flow down gradient of the source, or a pool, or both, or (during drought conditions) an area characterized by the presence of a mesic plant community (refer to Facultative-wet or Obligate plant species as listed in the National List of Plant Species That Occur in Wetlands, South Plains, Region 6, U.S. Department of the Interior, Washington D.C.)

2. standard setback - 150' radius around spring

CEF Buffer Zones: LDC, Section 25-8-281 C, 1a

3. administratively approved modified setback - same square footage as standard setback with 50' minimum below spring and square foot balance applied up gradient or area contributing to the spring 4. the Director may grant an administrative variance to further reduce setbacks for CEFs; however, the applicant for a variance must demonstrate that the proposed measures used in place of setbacks preserve all characteristics of the CEF

LDC, Section 25-8-281 (D)

(b) bluffs

1. are defined as an abrupt vertical change in topography of more than 40 feet with an average slope steeper than four feet of rise for one foot of horizontal travel (400 % or 76 degrees)

2. standard setback - 150' radius around the bluff

CEF Buffer Zones: LDC Section 25-8-281, C1a

3. administratively approved modified setback - same square footage as standard setback with 50' minimum below bluff and square foot balance applied up gradient of bluff

4. the Director may grant an administrative variance to further reduce setbacks for CEFs; however, the applicant for a variance must demonstrate that the proposed measures used in place of setbacks preserve all characteristics of the CEF

LDC 25-8-281 (D)

1. are defined as an abrupt vertical rock outcrop of more than 60% slope (31 degrees), greater than 4 feet vertically, and a horizontal extent equal or greater than 50'

2. standard setback - 150' radius around rimrock

CEF Buffer Zones: LDC Section 25-8-281, C1a

3. administratively approved modified setback - same square footage as standard setback with 50' minimum below rimrock and square foot balance applied up gradient of rimrock.

LDC 25-8-281 (D)

(d) caves 1. are defined as underground voids large enough for an adult to enter.

Point Recharge Identification Criteria: Environmental Criteria Manual (ECM) Section 1.10.0 - 1.10.3, & 1.10.4, C1

2. significance is determined by following the evaluation protocol, ECM Section 1.10.4, A & B

3. standard setback - 150' to 300' radius around surveyed surface projection of the cave footprint. (LDC Section 25-8-281, and ECM Section 1.10.4, C, 3, and Figures 1- 61, 1-62, 1-63 ECM Appendix V)

4. administratively approved modified setback - same square footage as the standard setback applied to the drainage area measured from the first break in slope at the cave entrance and/or surface projection of the cave footprint (LDC 25-8-281 (D;)ECM Section 1.10.4, C2)

5. the Director may grant an administrative variance to further reduce setbacks for CEFs; however, the applicant for a variance must demonstrate that the proposed measures used in place of setbacks preserve all characteristics of the CEF

LDC 225-8-281 (D)

6. guidance for protection of caves in undesirable pre-existing conditions is provided in the ECM Section 10.10.4, C, 5

(e) sinkholes and recharge features

1. are defined as a circular or oblong depressions formed in soluble rock by the action of subterranean water which is a potential point of significant recharge (with or without a surface opening)

Point Recharge Identification Criteria: ECM Section 1.10.0 - 1.10.3, & 1.10.4, C1

2. significance is determined by following the evaluation protocol, ECM Section 1.10.4, A & B

3. standard setback - 150' to 300' radius around surveyed around surface delineation of feature measured from the first break in slope (LDC Section 25-8-281, and ECM Section 1.10.4, C, 3, and Figure 1-61, 1-62, 1-63 ECM Appendix V)

4. administratively approved modified setback - same square footage as the standard setback applied over the drainage area to the sinkhole or fracture (LDC 25-8-281 (D); ECM Section 1.10.4, C, 2) 5. the Director may grant an administrative variance to further reduce setbacks for CEFs; however, the applicant for a variance must demonstrate that the proposed measures used in place of setbacks preserve all characteristics of the CEF

LDC 25-8-281 (D)

6. guidance for protection of sinkholes in undesirable pre-existing conditions is provided in the ECM Section 10.10.4, C, 5

(f) wetlands (LDC, Section 25-8-282)

1. are defined as lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. An area shall be classified as a wetland if it meets the Army Corps of Engineers three parameter technical criteria as outlined in the Corps of Engineers 1987 Wetlands Delineation Manual (Section D. Routine Determinations): a. three parameters for wetland determination include prevalence hydrophytic vegetation, hydric soil formation, and presence of adequate hydrology b. recommended routine method: wetland hydrology and hydric soils can be assumed if an area under examination is dominated (over 50% vegetative cover) by Facultative- wet and/or Obligate plant species as listed in the National List of Plant Species That Occur in Wetlands, South Plains, Region 6, U.S. Department of the Interior, Washington D.C.; and an abrupt boundary is evident between Facultative-wet and/or Obligate plant communities and Upland plant communities c. if the area is dominated by Facultative plant species, the hydric soil and hydrology parameters cannot be assumed; therefore, are also required for determination as a wetland

the area is not a wetland if dominated by Upland plant species, soils that are not hydric, or hydrology that is not wetland d. exceptions include permitted water quality wet ponds, roadside ditches, and ponds fed by wells or other artificial sources of hydrology e. potential wetlands are mapped on the U.S. Department of Interior, Fish and Wildlife Department, National Wetland Inventory Quad Maps; however, these areas must meet the Army Corps 1987 Delineation Manual criteria before classified as CEFs reference:

(USFWS) US Fish and Wildlife Service. 1993. National Wetland Inventory Map. Austin Area Quads. U.S. Department of the Interior, Washington, D.C.

2. standard setback - 150' around the outside edge of the wetland area; appropriate for wetlands fed by sheet flow from all directions. LDC Section 25-8-281 3. administratively approved modified setback - same square footage as the standard setback applied to the natural drainage patterns above and below the wetland; appropriate for fringe wetlands along streams or ponds in-line with streams.

LDC 25-8-281 (D)

5. wetland mitigation – minimum 1:1 replacement of same square footage as wetland CEF and standard 150' setback; appropriate for isolated wetlands whose source of hydrology will be compromised by the proposed development

Wetland replacements must be approved by the Director of Watershed Protection and Development Review. Replacements may include but are not limited to the following examples: a. on-site constructed wet ponds (for direction see ECM, Section 1.6.6, Design Guidelines For Wet Ponds) b. on-site detention ponds landscaped with a native wet prairie (for direction see COA Standard Specification Manual, Section 609S, Native Grassland Seeding and Planting For Erosion Control) c. additional on-site buffers around existing water features or CEFs d. on-site bio-filtration + infiltration enhancement of standard sedimentation/filtration water quality and/or detention ponds (consists of replacing most of sand bed or detention basin with wet prairie landscape over porous soil, over gravel infiltration substrate)

6. wetland restoration or enhancement for water quality controls; appropriate for existing ponds in-line with unclassified waterways or isolated ponds that can treat a development's storm water runoff (ECM, Section 1.6.6)

(2) Provide an environmental justification for spoil disposal locations or roadway alignments . The environmental assessment should identify inappropriate spoil disposal areas or roadway alignments, if present, to be considered during the Site Development phase or Construction Plan phase.

(a) spoil disposal sites (for guidance see LDC, Sections 25-8-323 and 25-8-343)

(b) roadway alignments are justified by selecting alternatives of least impact to environmental resources or sensitive areas including, trees (LDC, Sections 25-8-602 through 25-8-627), stream crossings (LDC, Section 25-8-262), and slopes (LDC, Sections 25-8-301 and 25-8-322) (3) Propose methods to achieve overland flow and justify enclosed storm sewers (LDC, Section 25-8-185). The environmental assessment should identify existing significant drainage patterns that support natural character, if present, for use in the Site Development phase or Construction Plan phase. Buffers around unclassified drainages may be employed as grassy filter strips for water quality credit where sheet flow can be maintained from adjacent impervious cover (For water quality credits see ECM, Section 1.6.7 F)

1.3.1 Hydrogeologic Element. See LDC Section 25-8-122.

(A) generally describe the topography, soils, and geology of the site

references may include USGS Topo 7.5' Quad Maps, USDA Soil Survey County Maps, Barton Springs/Edwards Aquifer Conservation District, 2003, 1:28,000 Geologic Map of the Barton Springs Segment of the Edwards Aquifer, and Bureau of Economic Geology Geologic Quad Maps

references:

Bureau of Economic Geology, University of Texas. 1992 Geologic Map of the Austin Area, Texas.

Garner, L.E., and K.P. Young. 1976. Environmental Geology of the Austin Area: An Aid to Urban Planning. The University of Texas at Austin, Bureau of Economic Geology.

Garner et al. 1976. Geologic Map of the Austin Area. Reprinted 1992. The University of Texas at Austin, Bureau of Economic Geology.

Proctor et al. Revised 1981. Geologic Atlas of Texas, Austin Sheet, Francis Luther Whitney Memorial Edition, University of Texas Bureau of Economic Geology.

(TECQ) Texas Commission on Environmental Quality. 2005. Edwards Aquifer Recharge Zone Boundary Maps. Chapter 213.

http://www.tceq.lstate.tx.us/compliaance/field _ops/eapp/program.html.

(TWDB) Texas Water Development Board, Water Well Drillers Records, March 2005.

USDA Soil Survey of Travis/Williamson/Hays County, Texas. Soil Conservation Service now Natural Resource Conservation Service, Temple Texas.

http://www.soildatamart.nrcs.usda.gov

(B) identify springs, bluffs, canyon rimrock, and point recharge features including caves , sinkholes, faults, solution cavities and enlarged fractures reference: ECM 1.3.0

a karst survey over the Edwards Aquifer Recharge Zone should be provided, consisting of 50' transects in a grid pattern across the project site completed by a Texas Licensed Geoscientist in the discipline of geology with experience in Central Texas

(C) demonstrate that proposed drainage patterns will protect the quality and quantity of recharge at significant point recharge features (ECM Section 1.10.4, C, 3, and Figure 1- 61, 1-62, 1-63 ECM Appendix V)